Electropneumatic brake



June 20, 1933. T. H. THQMAS 1,914,623

ELECTROPNEUMAT I C BRAKE Filed July 1928 2 Sheets-Sheet 1 ATTORNEY June20, 1933. T H TH MAS 1 914523 ELECTROPNEUMATIC BRAKE Filed July '7, 19282 Sheets-Sheet 2 Q g MI HI I INVENTOR THOMAS H.THOMA$ I A TORNEY IFatented June 20, 1933 PATET GFFEE THGMAS H. THQMAS, OF EDGEVIOOID,PENNSYLVANIA, ASSIGNDR' TO THE WESTING- AIR BRAKE CQMPANY, OFVJILE'IERDIHG, PENNSYLVAN 1A, A. CORPORATION or rnnivsvtvanraApplication filed July '3', 1928.

This invention relates to railway tratlic controlling apparatus and moreparticularly to the type controlled by energy received from thetrackway. V

The principal object of my invention is to provide an improved trainstop apparatus of the above type.

Other objects and ac vantages will appear in the following more detaileddescription of my invention.

In the accompanying drawingsyFig. 1 is a diagrammatic view of tirepneumatic apparatus embodying my invention; Fig. 2 is a diagrammaticview of a portion of the electric apparatus adapted to control the operation of the pneumatic apparatus shown in Fig. 1; and Fig. 3 isadevelopment view of the brake valve device shown in Fig. 1.

As shown in Fig. 1 of the drawings, the pneumatic apparatus may compr'sea brake valve device 1, a cut-oil valve device 2, a reduction limitingvalve device 3 and a ma gnet valve device.

The brake valve device 1 comprises a casing having a chamber 5containing a rotary valve 4 adapted to-be operated by a handle 6, andalso contained in the casing is the usual equal zing discharge valvemechanism comprising a piston 7 and a. discharge valve 8 adapted to beoperated by said piston. The piston 7 has at one side a chamber 9, whichis connected through a passage 10 and a choke plug 11 to an equalizingreservoir 12 and at the opposite side a chamber 13which is connectedthrough passage 14 to the brake pipe 15.

The cut-oft valve device 2 comprises a casing having a longitudinal boreclosed at the opposite ends by cap nuts 1? and 17, and contaiuing anapertured partition wall 18 having screw-threaded engagement in the wallof said bore. The partition wal 18 forms at one side a chamber 19containing apoppet valve 20., which 54 carried and operated by a stem21. which extends through the aperture ELECTROPNEUIVEATIC BRAKE SerialNo. 290,917.

ing to maintain the poppet valve 20 away from a seat ring 26,circumferentially formed about the aperture in partition wall 18.

The reduction limiting valve device 3 comprises a diaphragm 27 and avalve 28 adapted to be operated by said diaphragm. The diaphragm 27 hasat one side a chamber 29 and at the opposite or lower side a chamber 30connected to the atmosphere through an atmospheric passage 31. The valve28 is contained in a chamber 32 which is connected through passage andpipe 33 to a reservoir 3% and has a tluted stem 35 extending upwardlythrough a bore in the partition wall 38 and into the chamber 30, whereinsaid stem engages the diaphragm 27. A spring 37 in chamber 32 urges thevalve 28 up wardly towards its seat.

The magnet valve device comprises a magnet 38 connected to wires 10 andall. and adapted to operate two double seat valves 43 and 44. The valve43 is contained in a chamber 5 and has a fluted stem extendingdownwardly into a chamber 46, wherein said stem engages the upwardlyextending fluted stem of valve 44, which is contained in a chamber at. Aspring 48 in chamber 47 engages valve ll, tending to seat said valve andunseat valve 43.

Upwardly projecting from and operable by the magnet 88 is stem 49carrying at its outer end a switch 50 adapted upon energization of themagnet 38 to bridge the contact ends of wires 51 and 52. Energization ofsaid magnet also seats valve 13 and unseats valve 44 at the same timethat the switch 50 is moved downwardly. lVhen the magnet is deenergizedby cutting cit the current flow through wires and 41, the spring 48seats valve 44, unseats valve 43 and shifts switch upwardly, therebydisconnecting wires 51 and 52.

The current for operating the magnet 38 is supplied by a battery 53, andthe circuit through said magnet is controlled by a cascade relaycomprising two relay magnets 54 and 55, which are adapted to operateswitches 56 and 57 respectively.

The magnet 54, as well as the magnet 55, is so designed as to be slowacting, that is, there is a time delay between the opening of thecircuit through said magnet and the operation of the switch 56controlled by said magnet. The circuit through the magnet 54 iscontrolled by the switch 57 carried by magnet 55, while the circuitthrough said latter magnet is adapted to be controlled by a manuallyoperated acknowledging switch comprising a handle 58 secured to andadapted to Operate two switch contact fingers 59 and 60. The circuitthrough magnet is further controlled by an acknowledging relaycomprising a magnet 61 and three contact fingers 62, 63 and 64 adaptedto be operated by said magnet.

A decoding relay, which operates according to the track condition orsignal indication, comprises a magnet 65 and two contact fingers 66 and67, the contact finger 66 being connected by wire 40 to the positiveterminal of the electric battery 53, while the contact finger 67 isconnected by wire 73 to the negative terminal of said battery. 1

A signal 69, )referably in the form of a light, is located in theoperators cab of a locomotive, and is so connected by wires 70 and 71 tothe acknowledging relay and decoding relay that normally, as when thetrack conditions are favorable, said light will be lit, but upon achange in track conditions, as from favorable to unfavorable, said lightwill go out.

In operation, when the track conditions are favorable, the decodingrelay magnet 65 is energized and therefore holds the contact fingers 66and 67 in the position shown in the drawings, while the'circuit throughthe acknowledging relay magnet 61 is open, since the contact finger 67of the decoding relay is in a position in which wire 72 from theacknowledging relay magnet 61 is disconnected from wire 7 3 leading tothe negative terminal of battery 53.

Vith the decoding relay magnet 65 energized, the acknowledging relaymagnet 61 deenergized and the acknowledging switch fingers 59 and 60 inthe normal position, as shown in the drawings, a circuit is closedthrough the cascade relay magnet 55 by way of wire 40 from the battery53, switch finger 66 of the decoding relay, wire 71, switch finger 63 ofthe acknowledging relay, wire 74, acknowledging switch finger 60, wire75, magnet 55, wire 76, acknowledging relay switch finger 64, Wire 70,decoding relay switch finger 67 and wire 73 to the negative pole ofbattery 53. Energization of magnet 55 shifts switch 57 so as to connectwires 40 and 77, thereby closing a circuit through the cascade relaymagnet 54 by way of wire 40 from the positive terminal of battery 53,switch 57 wire 7 7, magnet 54 and wire 73 connected to the negative poleof battery 53. The magnet 54 is thus energized and causes switch 56 tooperate and connect Wires 41 and 73, thereby closing a circuit throughthe application magnet 38, by way of wire 40, application magnet 38,wire 41, switch 56, wire 73 and the battery 53, thus energizing saidapplication magnet.

WVith the apparatus in the clear track condition above described, thecab signal light 69 is lighted, since the light wires 71 and 70 areconnected to the opposite poles of battery 53 through the contactfingers 66 and 67 of the decoding relay and wires 40 and 73.

lVhen the application magnet 38 is energized, the switch 50 connects thewires 51 and 52 and also seats valve 43 and unseats the valve 44.

Fluid under pressure is supplied from a main reservoir 79 through a pipeand passage 80 to the rotary valve chamber 5 of the brake valve deviceand from pipe 80 to a feed valve device 81, which reduces the pressureof the fluid from that carried in the main reservoir to that normallycarried in the brake pipe. Fluid at this reduced pressure then flowsthrough pipe and passage 82 to the seat of the rotary valve 4.

ith favorable or clear track conditions and with the brake valve handle6 in the usual running position, fluid at feed valve pressure ispermitted to flow from passage 82 to the cut-off valve piston chamber 24through cavity 83 in the rotary valve 4, passage and pipe 84, magnetvalve chamber 47, past the unseated valve 44, through chamber 46 andpassage and pipe 85 and then from the piston chamber 24 to theequalizing piston chamber 9 by way of passage and pipe 86, past the ballcheck valve 87 in the brake valve device and through passage and pipe 10and from thence through the choke plug 11 to the equalizing reservoir12.

At the same time that the equalizing piston chamber 9 is charged, fluidat feed valve pressure flows through cavity 83 in the rotary valve 4 ofthe brake valve device and passage and pipe 88 to the cut-off valvepiston chamber 23. The fluid pressures therefore become equal on theopposite sides of the cut-off valve piston 22, and permit spring 25 tomaintain the cut-off valve piston 22 and cut-off valve '20 in theposition shown in the drawings, in which fluid at feed valve pressure ispermitted to flow from piston chamber 23 to the brake pipe 15 throughthe aperture in the partition wall 18, and the cut-off valve chamber 19.The equalizing piston chamber 13 in the brake valve device beingconnected to the brake pipe 15 becomes charged to the brake pipepressure, and since the pressures on the opposite sides of theequalizing piston are therefore substantially equal, said piston holdsthe discharge valve 8 seated, in the usual manner.

lVith the brake valve device in running position, fluid under pressureflows from the rotary valve chamber 5 through port 89 in the" rotaryvalve 4 and passage and pipe 90 to diaphragm chamber 29 of the reductionlimiting valve device and therein acts on diaphragm 27, causing saiddiaphragm to deflect downwardly and unseat valve 28, which then normallyconnects the reduction limiting reservoir 34 to the atmosphere throughpipe and passage 33, valve chamber 32, past theunseated valve 28,through diaphragm chamber 30 and the atmospheric passage 31.

If the track conditions become unfavorable, the decoding relay magnet 65becomes deenergized, thereby permitting the contact fingers 66 and 67 todrop and connect the wires 52 and 72. This interrupts the circuit to thecab signal light 69 through wires 70 and 71, causing the signal lightto. go out, so as to reveal to the engineer the unfavorable trackconditions.

Since the circuit through the cascade relay magnet 55 is normallyclosedin the same manner that the cab signal light circuit is closed, thechange in signal indication causes said magnet to become deenergized.However, the energizing circuit through the eascade relay magnet 54remains closed for a period of time, since in accordance with the designof magnet 55, there is a predetermined time lapse between the opening ofthe circuit through said magnet and obtaining suficient deenergizationthereof to permit the switch 57 to shift and disconnect the wires 40 and77 and thus open the circuit through the magnet 54. Then after anotherlapse of time, suflicient to deenergize magnet 54, the switch 56 movesdown and opens the circuit through the application magnet 38. The reasonfor the delay in deenergization of magnets 54 and 55 after the circuitthrough said magnets is opened, will be hereinafter described.

Deenergization of the applica ion magnet 38 permits spring 48 to seatvalve 44, unseat valve 43 and shift switch 50 upwardly, so as todisconnect the wires 51 and 52.

The seating of valve 44 cuts off the supply of fluid at feed valvepressure from passage 84 to passage 85 and thence to the cut-off valvepiston chamber 24 and the equalizing resevoir 12, while unseating ofvalve 43 permits fluid under pressure tic-quickly flow from said cut-offvalve piston chamber through passage and pipe 85, chamber 46 in theapplication magnet valve device, past the unseated Valve 43 and thencethrough pipe 33 to the reduction limiting reservoir 34. Fluid at feedvalve pressure in the cut-oil valve pis ton chamber 23 then shifts thecut-off valve piston outwardly against the reduced pres sure of thefluid in chamber 24 and the resistance of spring 25, thereby causing thecut-off valve 20 to seatagainst the seat ring 26 and prevent furtherflow of fluid at feed valve pressure from chamber 23 to chamber 19 andthence tothe brake pipe 15.

Since the equalizing piston chamber 9 and equalizing reservoir 12 areconnected to the cut-off valve piston chamber 24 through pipe 10, chokeplug 91 and passage and pipe 86, the pressure in chamber 9 reduces at arate governed by the flow area of said choke plug, which is such as topermit the pressure in the cut-oil valve piston chamber 24 to remain ata low degree, so as to prevent reopening of the cut-off valve 20.

The reduction in pressure in the equalizing piston chamber 9 permits thepressure of the fluid from the brake pipe in the equalizing pistonchamber 13 to shift the equalizing piston 7 upwardly and open the brakepipe discharge valve 3, thereby permitting fluid under pressure to flowfrom the brake pipe 15 to the atmosphere and thus cause a brake pipereduction and consequent application of the brak s in the usual wellknown manner.

As shown in the drawings, with the brake valve handle 6 in runningposition, the reduction limiting valve 28 is normally maintainedunseated by the fluid under pressure acting on diaphragm 27 in chamber29. Under such a condition the reduction limiting reservoir 34 isconnected to the atmosphere as hereinbefore described, so that when anautomatic application of the brakes occurs, the fluid under pressure iscompletely vented from the equalizing reservoir 12 to the atmosphere andconsequently permits a total venting of fluid under pressure from thebrake pipe 15.

If it is desired to prevent a total venting of fluid under pressure fromthe brake pipe as just described, then upon initiation of the brakeapplication, the brake valve handle 6 is moved to lap position, in whichthe reduction limiting valve diaphragm chamber 29 is vented to theatmosphere through pipe and passage and the atmospheric passage 92 byway of a cavity (not shownl in the rotary valve 4 which, in lap positionof the handle 6, is adapted to connect the passages 90 and 92.

Venting of the diapln'agm chamber 29 permits spring 37 to seat the valve28, so that when an automatic application of the brakes is effected, ashereinbefore described, the reduction in equalizingreservoir pressure islimited to equalization of pressures in the equalizing reservoir 12 andthe reduction limiting reservoir 34, it being noted that the enga ementof the valve 20 with its seat prevents piston frcm moving to the leftsufliciently to close the pass ge 35. Such a lim ited reduction inequalizing reservoir pressure permits a sullicient decrease in brakepipe pressure, effective in the equalizing piston chamber 13, to make afull service application of the brakes.

If, for any reason, it is desired to effect an application of the brakesby Operation of the brake valve device 1 in the usual manner, instead ofpermitting the application to be automatically effected hereinbeforedescribed, then, when the decoding relay magnet becomes deenergized dueto the change in trai'lic conditions, and the cab signal light 69 goesout, as hereinhefore described, the operator shifts the acknowledgingswitch contacts 59 and 60 downwardly by movement of the handle 58.

In the downward position of the acknowledging switch, the contact 60disconnects wires and 7-1 through which the circuit to the cascademagnet 55 was closed prior to deenergization of the decoding relaymagnet 65. In this downward position, the other switch contact 59connects wires 51 and 93, thereby closing a circuit through theacknowledging relay magnet 61 by way of wire 40 from the positiveterminal of battery 53, switch arm 66 of the decoding relay, wire 52,the application magnet switch 50, wire 51, acknowledging switch arm 59,wire 93, acknowledging relay magnet 61, wire 72, decoding relay switcharm 67 and wire 73 leading to the negative pole of battery 53.

Closing a circuit through the acknowledging relay magnet 61 energizessame, which causes the switch arms 62, 63 and 64 to be pulled upwardly.The arm 62 then connects with wire 40 from the positive terminal of thebattery 53, thus permitting current to flow from said battery throughthe relay magnet 61, wire 72, decoding relay switch arm 67 and wire 7 3to the negative pole of battery 53, thereby closing a second circuitthrough the acknowledging relay magnet 61. The acknowledging switch arms59 and 60 are then returned to the normal position as shown in' thedrawings, and the acknowledging relay magnet 61 remains energized.

When the acknowledging switch is returned to its normal position andwith the acknowledging relay magnet 61 energized as just described, thecircuit is again closed through the cascade relay magnet 55 by way ofwire 4.0 from the positive terminal of the battery 53, acknowledgingrelay magnet switch arm 63, wire 74, acknowledging switch arm 60, wire75, cascade relay magnet 55, wire 76, acknowledging relay magnet switcharm 64 and wire 73 from the negative pole of battery 53. Reclosing thecircuit through magnet 55 closes the circuit through magnet 54 in casethe latter circuit is opened. Magnet 54 then being energized maintainsthe application magnet 38 energized.

It should be noted that the circuit through the cascade relay magnet 55is opened as soon as the decoding relay magnet 65 is deenergized, butthat the application magnet 38 is not deenergized until a predeterminedtime after the deenergization of said decoding relay magnet 65 by achange in signal indication in the manner hereinbefore described. It isduring this time period that the engineer must acknowledge the change insignal indication, if he wishes to initiate the brake applicationinstead of permitting the application to be automatically made in themanner hereinbefore described.

In acknowledging a change in signal indication, the circuit closed inenergizing the acknowledging relay magnet 61 is controlled through theapplication magnet switch 50, so that in case the engineer fails toacknowledge before deenergization of the magnet 38 and the consequentupward movement of switch 50, then the brake application is causedautomatically in the manner hereinbefore described and is thus out ofthe control of the engineer.

Assuming that the change in signal indication is properly acknowledgedby the engineer before deenergization of the application magnet 38, thenin order to manually effect an application of the brakes, the brakevalve handle is operated to turn the rotary valve a to service position,in which the equalizing piston chamber 9 and equalizing reservoir 12 areconnected to the atmosphere through passage 10, choke plug 91, passage86, a cavity (not shown) in the rotary valve 4- and the atmosphericpassage 92. The flow area of choke plug 91 is less than that of chokeplug 11, so that the pressure in said equalizing piston chamber andreservoir remains substantially equal during a reduction in pressuretherein.

Reducing the pressure in the equalizing piston chamber 9 permits thehigher brake pipe pressure in the equalizing piston chamber 13 to shiftthe equalizing piston 7 upwardly and unseat the brake pipe dischargevalve 8, which then permits fluid under pressure to flow from the brakepipe 15 to the atmosphere by way of passage 14, chamber 13 and pipe andpassage 95.

When the brake pipe pressure is reduced a degree equal to the degree ofreduction in equalizing reservoir pressure, the equalizing piston 7operates to close the discharge valve 8 in the usual well known manner.

In order to release an application of the brakes caused by operation ofthe brake valve device, the brake valve handle 6 is turned to runningposition in which the brake pipe 15, and the equalizing reservoir 12 arerecharged in the same manner as hereinbefore described.

In case a brake application is automatically effected due to unfavorabletrack conditions, such an application can not be released until thetrack conditions become favorable again, which then causes the decodingrelay magnet 65 to become reenergized so as to effect the return of theswitch arms 66 and 67 to their normal position as shown in the drawings,

in which position, wires 72 and 73 are disconnected, thereby opening thecircuit through the acknowledging relay magnet 61. S'aid magnetisthereby deenergized, which permits the switch arms 62, 63 and 6% todrop to their normal position. With the decoding and acknowledging relaymagnets and 61, respectively, returned to their normal positions and thebrake valve handle 6 in running position as shown in the drawings, thebrakes are released by recharging the brake pipe 15 in the same manneras hereinbefore described.

A double heading cock 96 is interposed in the pipes 88 and 95 in such amanner that the flow of fluid under pressure through said pipes may becontrolled through a plug valve 97, which may be turned by a handle 98to either the position shown in the drawings, in which communication ispermitted through pipe 88 and from pipe 95 to the atmosphere, or to asecond position in which such communication is cut off. This isdesirable under certain conditions, as will be now explained.

In the case of double heading, the brake cont-rolling apparatus on thesecond locomotive is cut out by means not shown and the applicationmagnet 38 is therefore deenergized. The double heading cock 96 isturned, so as to close communication through pipe 88 and from pipe 95 tothe atmosphere on said second locomotive, so that with the equalizingpiston chamber 9 vented to the atmosphere by way of the unseated magnetvalve 43, and the discharge valve 8 unseated by the brake pipe pressurein the equalizing piston chamber 13, fluid under pressure-can not flowfrom the brake pipe 15 to the atmosphere and thus interfere with thecontrol of brake pipe pressure on the leading locomotive.

If only the brake pipe discharge passage 95 were controlled through thedouble heading cock 96, as just described, then the engineer couldprevent an automatic application of the brakes from occurring by'merelyoperating a locomotive with said cock in the closed position and thenturning said cock to the open position only when he desired that anapplication should be made. In order to prevent such undesiredoperation, the supply of fluid under pressure to the brake pipe, by wayof passage and pipe 88, is also controlled through said cock, so that inorder to charge the brake pipe 15 and maintain the pressure therein soas to prevent brake pipe leakage from applying the brakes, the doubleheading cock has to be in the open position, as shown in the drawings,in which the brake pipe discharge passage 95 is also open.

It will be noted that the time from the change in signal indication: tothe deenergization of the application magnet 38, during which theengineer may acknowledge in order to efiect a brake applicationmanually, is

equal to the sum of the lag or delay in deenergization of the cascaderelay magnets 55 and 54 from the time the circuits through said magnetsis opened. For instance, there may be a two second delay from the timethe circuit through magnet 55 is opened until the downward movement ofthe switch. With a like delay in magnet 5% there would be a 4 secondtime interval between the change in signal indication and opening of thecircuit through the application magnet 38. Thus according to the timeinterval desired, the number of magnets used, similar to 54 and 55, maybe varied, or the design of said magnets may be changed in order toefi'ect the delay desired.

The choke plug 11 is provided in passage 10, leading to the equalizingreservoir 12, so that in charging, the fluid under pressure flowing pastthe ball check valve 87 into the equalizing piston chamber 9 willquickly build up a pressure therein ahead of the build-up of pressure inthe equalizing reser voir 12, so as to preventthe brake pipe pressurebuild-up in equalizing piston chamber 13 from raising the equalizingpiston 7 and thereby unseating the discharge valve 8 and permittingfluid under pressure to flow from the brake pipe to the atmosphere.

From the foregoing description of operation, it will be noted that whenthe traffic conditions change from favorable to unfavorable, thedecoding relay magnet 65 is deenergized and opens a circuit through theslow acting relay magnet 55. Upon deenergization of relay magnet 55, acircuit through the slow acting relay magnet 54: is

opened, which in turn operates to open a circuit through the applicationmagnet 38. Upon. deenergization of the application magnet 38, thecut-off valve device 2 operates to out Oh the supply of fluid underpressure to the brake pipe 15 and the equalizing piston 7 and brake pipedischarge valve 8 operate to effect a reduction in brake pipe pressureand cause an application of the brakes to be efiected.

The equalizing piston 7 operates upon a reduction in equalizingreservoir pressure in piston chamber 9, the pressure in the equalizingreservoir 12 reducing by flow to the reduction limiting reservoir 34.With the reduction limiting reservoir open to the atmosphere through thereduction limiting valve device 3, as when the brake valve device is inrunning position, a complete venting of fluid from the equalizingreservoir and consequently from the brake pipe results.

In order to limit the brake pipe reduction to only that required toeltect a full service application of the brakes, the engineer can turnthe brake valve device from running position to lap position. By sodoing, the reduction limiting valve devlce 3 operates to close theatmospheric connection to the reduction limiting reservoir. As a result,the reduction in equalizing reservoir pressure is limited toequalization in the reduction limiting reservoir, and a brake pipereduction of corresponding degree is effected in the usual well knownmanner. After a train control application of the brakes is effected inthe manner just described, the brakes can not be released until afterthe traflic conditions become favorable and the decoding magnet is againenergized.

In order to avoid the possible delay in schedule caused by a traincontrol application of the brakes, the engineer may prevent a traincontrol application of brakes and apply the brakes in the usual mannerby the brake valve device and then proceed With caution.

In order to apply the brakes by operation of the brake valve device 1instead of permitting the train control apparatus to apply the brakes,the engineer shifts the acknowledging switch contacts 59 and 60 to theirlower-position after the decoding relay magnet 65 becomes deenergized.In the lower position of the acknowledging switch contacts, a stickcircuit is closed through the acknowledging relay magnet 61, after whichthe acknowledging switch contacts are returned to their normal positionfor reclosing the circuit through the cascade relay magnet 55, theenergization of magnet 55 thereby preventing the deenergization of theapplication magnet 38. It will however be noted that the stick circuitthrough the acknowledging relay magnet 61 is controlled by theapplication magnet switch 50, so that if the application magnet isdeenergized at the time the acknowledging switch contacts 59 and 60 aremoved to their lower position, the train control application of brakescan not be stopped. There is, however, a delay period between thedeenergization oi the decoding relay magnet 65 and the deenei.-gizationof the application magnet 38, which is measured by the additive slowaction of the cascade relay magnets 55 and 54, and it is during thisperiod that the engineer must acknowledge to close the stick circuitabove mentioned.

When the engineer properly acknowledges the change in traflicconditions, he moves the brake valve device to service position, inwhich a service application of the brakes is effected in the usualmanner.

In addition to the above, a choke plug 11 is provided to restrict thecharging of the equalizing reservoir 12 so as to hasten the build up ofpressure in chamber 9 on the equalizing piston 7 in order to prevent thebuild up of brake pipe pressure in chamber 13 from shifting theequalizing piston 7 to open the brake pipe discharge valve 8 andcauseundesired venting of fluid under pressure from the brake pipe. A chokeplug 91 is provided to restrict the flow of fluid under pressure fromthe equalizing reservoir to chamber 245 of the cut-oil' valve device 2when a train control application of the brakes is efl ected, so as toprevent a suflicient pressure to be obtained in said chamber to cause anundesired opening of the cutoff valve 20.

lVhile one illustrative embodiment of the invention has been describedin detail, it is not my intention to limit its scope to that embodimentor otherwise than by the terms of the appended claims.

Having now described my invention, what I claim as new and desire tosecure by Letters Patent, is

1. In an electro-pneumatic brake, the combination with a brake pipe anda magnet valve device, of a cut-oil valve device controlled by saidmagnet valve device and 0perative upon energization of the magnet ofsaid magnet valve device to supply fluid under pressure to said brakepipe and operative upon deenergization of said magnet to cut oil thesupply of fluid under pressure to said brake pipe, and an equalizingvalve mechanism operative upon deenergization of said magnet to ventfluid under pressure from said brake pipe.

2. In an electro-pneumatic brake, the combination with a brake pipe anda magnet valve device, of a valve for controlling the supply of fluidunder pressure to said brake pipe, a piston for operating said valve,said piston being controlled by said magnet valve device, another valvefor venting fluid under pressure from said brake pipe, and a pistoncontrolled by said magnet valve device for operating the last mentionedvalve.

3. In an electro-pneumatic brake, the combination with a brake pipe, ofa discharge valve for venting fluid under pressure from said brake pipe,an equalizing piston for operating said discharge valve, a cutoli' valvefor supplying fluid under pressure to said brake pipe, a piston foroperating said cutoff valve and subject on one side to fluid underpressure, a magnet, a valve operative upon energization of said magnetto supply fluid under pressure to one side of said equalizing piston forclosing said discharge valve and to supply fluid under pressure to theother side of said cut-off valve piston, a spring for opening saidcut-off valve to sup- 7 ply fluid under pressure to said brake pipe whenthe opposite sides of the cut-off valve piston are subject to fluidunder pressure, and another valve operative upon deenergization of saidmagnet to vent fluid under pressure from the one side of said equalizingpiston for opening said discharge valve to vent fluid under pressurefrom said brake pipe, said other valve being also operative upondeenergization of said magnet to vent fluid under pressure from one sideof the cut-otl valve piston for closing said cub-oil valve.

4. In an electro-pneumatic brake, the combination with a brake pipe, ofa discharge valve for venting fluid under pressure from said brake pipe,an equalizing piston tor op erating said discharge valve, an equalizingreservoir connected to a chamber at one side of said equalizing piston,a magnet, valve operative upon energization of said magnet to supplyfluid under pressure to said equalizine; reservoir and to said chamber"for operating the equalizing piston to close said discharge valve,means for restrict ng the supply of fluid under pressure to sa dequalizing reservoir, another valve operative upon deenergization ofsaid magnet for venting fluid uiider pressure from said chamber andequalizing reservoir, and means for restricting the venting of fluidunder pressure therefrom.

5. in an electi pneumatic brake, bination with a brake pipe, oil? avalve for venting fluid under said b ake pipe, an equalioing cratingsaid discharge valve, V reservoir connected to a chamber at one side ofsaid equalizing piston, a magnet, a valve operative upon energization omagnet to supply fluid under pressure to said equalizing reservoirthrough a restricted passage and to chamber through an unrestrictedpassage, and another valve operative upon deenergization of said magnetfor venting fluid under pressure from said chamber and equalizingreservoir through another restricted passage.

6. In an electro-pneumatic brake, the combination with a brake pipe anda hralte valve device. of a magnet valve device "for effecting areduction in brake pipe pressure, and means associated with said magnetvalve device operative in accordance with the position oi said brakevalve device for controlling the degree of reduction in brake pipepressure.

7. In an electro-pneumatic brake, the combination with a brake pipe anda brake valve device, of a magnet valve device for effecting a reductionin brake pipe pressure, and means associated with said magnet valvedevice operative to completely vent the fluid under pressure from thebrake pipe when said brake valve device is in one position, and to limitthe degree of brake pipe reduction zen said brake valve device is inanother position.

8. In an electro-pneumatic brake, the combination with a brake pipe,reduction limiting reservoir and a brake valve device, of a magnet Valvedevice for venting fluid under pressure from said brake pipe to saidreservoir, and a valve controlled by said brake valve device forcontrolling communication from said reservoir to the atmosphere.

9. In an electro-pneumatic brake, the combination with a brake pipe anda brake valve device, of an equalizing valve mechanism for venting fluidunder pressure from said brake pipe, an equalizing reservoir normallycharged with fluid under pressure for govorning the mechanism, a magnet,a valve operative upon energization of said magnet for supplying fluidunder pressure to said equalizing reservoir and upon deenergization ofsaid magnet to cut oil the supply of fluid under pressure to saidreservoir, a reduction limiting reser voir, another valve operative uponenergization of said m gnet for closing a connection from said equ.izing reservoir to said reduc-. tion limiting reservoir and upondeenergization oi said magnet to vent fluid under pressure from saidequalizing reservoir to said reduction limiting reservoir, and pressuresensitive means normally establishing a communication through which saidreduction limiting reservoir is vented and having a position for closingsaid communication, said brake valve device being operative to controlthe operation or said pressure sensitive means.

10. In an electro-nneiunatic brake, the combination with a brake pipeand a brake valve device, of an equalizing valve mechanism for ventingfluid under pressure from said brake pipe, an equalizing reservoirnormally charged with fluid under pressure for governing the operationof said equalizing valve mechanism, a magnet, a reduction limitingreservoir, valve means operated upon energization of said magnet tosupply fluid under pressure to said equalizing reservoir and upondeenergization of said magnet to vent fluid under pressure from saidequalizing reservoir to said reduction limiting reservoir, and valvemeans operative in accordance with the position of said brake valvedevice t'or controlling an atmospheric communication from said reductionlimiting reservoir to the atmosphere.

11. In an electro1: neumatic brake, the col'nbination with a brake pipe,of valve means for controlling the supply of fluid under pressure to andthe venting of fluid un der pressure from said brake pipe,electroresponsive means for controlling said valve means, and a valvedevice for controlling the communication through which fluid underpressure is supplied to the brake pipe and the communication throughwhich fluid under pressure is vented from the brake pipe, said valvedevice being operative to close said communications.

1:2. In an electropneumatic brake, the combination with a brake pipe, ofa valve device for controlling the supply of fluid under pressure tosaid brake pipe and operated by a variation in fluid pressure to cutoil" the supply of fluid under pressure to said brake pipe, a valvedevice operated by a variation in fluid pressure to vent fluid underpressure operation of said equalizing valve from the brake pipe, andelectro-responsive means for varying the fluid pressure on said valvedevices.

13. In an electro-pneumatic brake, the

combination With a brake pipe, of a cut-ofl valve for controlling thesupply of fluid under pressure to the brake pipe, electroresp0nsivemeans for operating said cut-0E valve device to cut oflthe flow of fluidunder pressure to said brake pipe, an equalizing valve mechanism forventing fluid under pressure from the brake pipe, and a manuallyoperated valve for controlling the communication through which fluid isvented from the brake pipe and the communication through which fluidunder pressure is supplied to the brake plpe.

14. In an electro-pneumatic brake, the combination with a brake pipe, ofelectroresponsive means for controlling the supply of fluid underpressure to and the venting of fluid under pressure from the brake pipe,and a manually operated valve having a position for closing thecommunication through which fluid under pressure is supplied to saidbrake pipe and the communication through which fluid under pressure isvented from the brake pipe by operation of said electro-responsivemeans.

In testimony whereof I have hereunto set my hand, this 2nd day of July,1928.

THOMAS H. THOMAS.

